1. Field of the Invention
The present invention relates to a photoelectric detector utilizing the light which is projected to and then reflected on an object to be detected to detect information such as presence or absence of said object or a distance to said object.
2. Background Art
There have already been proposed the photoelectric detectors of various arrangements utilizing the reflected light from the object to be detected, an example of which is illustrated by FIG. 10 of the accompanying drawing.
In accordance with this prior art, light is projected from a light emitting diode 11 to an object 12 to be detected and the light reflected on said object 12 is received by a phototransistor 13.
With this photoelectric detector, it is possible to detect the presence of the object 12 to be detected, so far as said object 12 is within a distance or range of d, and once an output threshold has been preset, it is possible to detect the maximum distance d.sub.max to the object 12 by determining when a photoelectric current from said phototransistor 13 is interrupted.
The above-mentioned detector of prior art, however, has encountered a serious problem that the intensity of reflected light depends on the characteristics of individual objects 12 to be detected, for example, the reflection factors and the reflecting surface configurations. Therefore, detection has been inconveniently limited to the particular objects 12 having certain characteristics because a value of the maximum distance d.sub.max depends on said characteristics.
Accordingly, such detector of well known art has been certainly effective for detection of a distance with respect to objects of a specific kind (particularly having a same reflection factor), but less reliable for detection of objects of different kinds.